docs: def _catalog_local_files_for_deletion(self):
          # type: (Downloader) -> None
          """Catalog all local files if delete extraneous enabled
          :param Downloader self: this
          """
          if not (self._spec.options.delete_extraneous_destination and
                  self._spec.destination.is_dir):
              return
          dst = str(self._spec.destination.path)
          for file in blobxfer.util.scantree(dst):
              self._delete_after.add(pathlib.Path(file.path))